(NewsNation) — Riley Strain’s fraternity brothers apparently attended a formal to party while his family searched for the missing Mizzou student, according to Michelle Whiteid, Strain’s mother.

Strain’s body was discovered March 22 in the Cumberland River in West Nashville, Tennessee. Nashville police said the college student’s death appears “accidental,” with no trauma suggesting foul play, according to preliminary autopsy results.

Strain’s frat brothers “all of a sudden disappeared, all of the boys,” during the search, Whiteid said. “A little later,” she added, they showed up “in their dress clothes to go out to their formal that night.” 

Riley Strain’s family talked to NewsNation’s Brian Entin about Riley’s fraternity brothers, his messages about his drink and more in an extended exclusive interview. Not sure how to watch NewsNation? Log in to this web player or go to JoinNN.com to locate us on your TV. 

In an emotional interview with NewsNation’s Brian Entin, Whiteid said on top of Strain’s friends choosing to party during the search, they apparently did not call 911 the night he went missing, either.

“Why wouldn’t they? Why wouldn’t they have called the police when they got back at 3:15 in the morning and didn’t see him then? Why wouldn’t they have called the police?” Whiteid said Tuesday on “Banfield.”

Strain’s family has ordered a second autopsy that they hope brings clarity.

Strain disappeared March 8 during a trip to Nashville with his Delta Chi fraternity brothers.

He communicated with his mom throughout the trip and texted her when they arrived at the hotel, she said. During the evening, Strain texted Whiteid saying he ordered a rum and Coke “that didn’t taste good.”

“Maybe there was something in it that shouldn’t have been,” Whiteid said. The TC Restaurant Group, which owns and operates the bar, said Strain was asked to leave after being served one alcoholic drink and two waters.

His toxicology results aren’t complete yet. It’s unclear what else, if anything, may have been in Strain’s system at the time.

The next morning, when Whiteid woke up to go grocery shopping, she received a call from his fraternity brother, asking if she’d heard from Strain.

His body was discovered two weeks later, about 8 miles from where he was last seen. Strain was missing his wallet, pants and boots. His family said he had been wearing a belt that night, which should have secured his pants.

Forensic pathologist Priya Banerjee and NewsNation law and justice contributor Jennifer Coffindaffer previously told NewsNation it’s difficult to make the “leap” that something “nefarious” happened to Strain.

“Eight miles is really long undercurrent,” Banerjee said.” I think you could lose things.”

Whiteid said she believes it’s possible Strain’s fraternity brothers have more details about the night her son went missing that they haven’t yet shared.

“I haven’t sat down with them. Would I like that? Yes, it would be nice” if Strain’s fraternity brothers would agree, she said. “We may never know what happened that night, but I would like to know everything that happened that day,” Whiteid added.

NewsNation’s Katie Smith contributed to this report.